Catchment header and membrane module unit

ABSTRACT

A catchment header allowing a plurality of membrane modules to be connected thereto, having a tubular catchment part with a Young&#39;s modulus of 4.0 GPa or less for collecting and taking out filtrated liquid from the membrane modules, wherein at least a part of the tubular catchment part is covered with a reinforcement member with a Young&#39;s modulus of 4.0 to 250 GPa, the tubular catchment part of the catchment header is preferably formed of a synthetic resin, and the cross sectional area thereof perpendicular to the longitudinal direction of the tubular catchment part is preferably 4 to 36 cm 2 .

TECHNICAL FIELD

The present invention relates to a catchment header allowing a pluralityof membrane modules to be connected thereto for collecting anddelivering filtrated liquid, and to a membrane module unit.

This application is based on Japanese Patent Application No. 2002-31414,the content of which is incorporated herein by reference.

BACKGROUND ART

Various methods have been studied to carry out a solid-liquid separationfor liquid to be treated using membrane modules provided with aseparation membrane, such as a microfiltration membrane and anultrafiltration membrane, in water treatment of sewage, drainage, etc.It is possible to obtain treated water of high quality when a filtrationprocess of liquid to be treated is carried out using a separationmembrane.

When a solid-liquid separation of liquid to be treated is carried outusing a filtration membrane, since clogging of separation membrane dueto suspended substances (SS) progresses as the filtration processcontinues, problems, such as reduction of filtration rate and increasein pressure difference between membranes, occur. In order to recoverfrom such state, a technique is known in which a diffuser is disposedbelow a membrane separation device and air is diffused during afiltration process or when a filtration process is stopped.

A method for carrying out a stable solid-liquid separation using ahollow fiber membrane module in which a hollow fiber membrane of a sheetshape is fixed to a rectangular housing using a resin so as to maintaina constant distance between adjacent membrane modules and air is bubbledfrom a diffuser so that flow of liquid to be treated is uniformlydirected to the membrane modules, is disclosed in Japanese Laid-OpenPatent Application, No. Hei 5-261253, Japanese Laid-Open PatentApplication, No. Hei 6-342, Japanese Laid-Open Patent Application, No.Hei 6-340, etc.

A method is known in which a plurality of membrane modules arefluid-tightly connected to a tubular catchment header having holes forconnecting to the membranes modules so that a constant distance ismaintained between adjacent membrane modules and filtered liquid iscollected and taken out from the membrane modules.

Various catchment headers have been proposed, such as one in which aresin flat plate having holes for connecting to modules is welded toresin pipes, one in which a metal thick plate having holes forconnecting to modules is welded to a metal thin plate which is bent tobe in a U-shape, and one in which a metal thick plate having holes forconnecting to modules is combined with a resin water passage part.

Although one in which a resin flat plate having holes for connecting tomodules is welded to resin pipes can be easily processed as comparedwith a metallic one, the mechanical strength of a resin pipe which formsa catchment part is weaker than that of a metallic pipe of the sameshape.

For this reason, when a catchment header is formed using a resin pipe,the outer diameter of a catchment header has to be made large in orderto resist bending stress applied to the catchment header during a bubblewashing, etc., for a long period of time. Accordingly, a portion of theheader which is not directly involved with a filtration process becomeslarge, and hence it is difficult to improve the catchment efficiency ofa membrane.

Also, when sludge attaches to the surface of a membrane due to some kindof problem and a membrane separation device is pulled out of water inorder to solve the problem, a bending stress which is larger than normalmay be applied to the catchment header and the header may be broken.Accordingly, it is necessary to increase the diameter of the catchmentheader so as to withstand a stress which is larger than normal to avoidthe breakage, and this leads to further decrease in the catchmentefficiency.

Moreover, although there are a catchment header in which a metal thickplate having holes for connecting to modules is welded to a metal thinplate which is bent to be in a U-shape, and in which a metal thick platehaving holes for connecting to modules is combined with a resin waterpassage part, it is necessary to carry out a process for continuouslyforming a plurality of holes for connecting to modules in a metal thickplate for these catchment headers and such a process is quite difficultto perform. Furthermore, as for welding to a metallic thin plate, it isnot easy to perform continuous welding without causing distortion in alongitudinal direction and, for example, 5 to 6 mm flexure would begenerated in both horizontal and vertical directions due to thermaldistortion of welding when a 70 cm catchment header is produced bywelding. Accordingly, it is difficult to orderly arrange a plurality ofmembrane modules with a distorted catchment header.

In addition, there is a danger that welding will become insufficient andthe welded portions may be separated during use of a long period oftime, causing leakage of liquid.

The present invention has been achieved in consideration of solving theabove-mentioned problems, and objects thereof include to provide alight-weight and compact catchment header which is excellent inworkability and is capable of carrying out a solid-liquid separationprocess using a separation membrane in a stable manner for a long periodof time.

DISCLOSURE OF INVENTION

Accordingly, the first aspect of the present invention provides acatchment header allowing a plurality of membrane modules to beconnected thereto, including: a tubular catchment part having a Young'smodulus of 4.0 GPa or less for collecting and taking out filtratedliquid from the membrane modules, and a reinforcement member having aYoung's modulus of 4.0 GPa to 250 GPa which covers at least a part ofthe tubular catchment part.

Also, it is preferable that the tubular catchment part be formed of asynthetic resin since it can be easily molded at low cost.

Also, it is preferable that a cross-sectional area of the tubularcatchment part perpendicular to a longitudinal direction of the tubularcatchment part be 4 to 36 cm² since the size thereof can be made compactyet a sufficient amount of filtrate can be passed through.

Also, it is preferable that the tubular catchment part include aplurality of members which are connected in series since an arbitrarylength of the catchment header can be obtained.

Also, it is preferable that the reinforcement member is formed of ametal, a filler reinforced plastic, or a fiber reinforced plastic sincethe strength thereof can be improved.

The second aspect of the present invention provides a membrane moduleunit, including: a plurality of membrane modules, and one of theabove-mentioned catchment header to which the plurality of membranemodules are connected.

Also, it is preferable that the membrane modules be hollow fibermembrane modules in which bundle ends of a hollow fiber membrane of asheet shape are accommodated inside a housing of a rectangular shape andfluid-tightly fixed using a fixing member since the catchment efficiencyof the membrane can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a perspective view of a catchment headeraccording to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional view of a catchment headeraccording to an embodiment of the present invention.

FIG. 3 is a diagram showing a perspective view of an example of a hollowfiber membrane module used in the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be explained in detail.

FIG. 1 is a diagram showing a perspective view of a catchment headeraccording to an embodiment of the present invention. In FIG. 1, atubular catchment part 1 includes a membrane module connection part 3 inwhich membrane module connection holes 2 are formed at the center. Theinside of the tubular catchment part 1 is hollow so that filtratedliquid from the membrane modules can be collected and passedtherethrough. A filtered liquid outlet 4 is disposed at one or both endsof the tubular catchment part 1.

It is preferable that the tubular catchment part 1 be formed using aresin since it becomes easy to process. Examples of the resin include athermoplastic resin, such as a vinyl chloride resin, a polyolefin resin,a polystyrene resin, an ABS resin, a polycarbonate resin, a polyamideresin, a polyester resin, a denatured polyphenylene ether resin, and apolyacetal resin. It is preferable to use a resin which does not containa reinforcement filler as a material for the tubular catchment part 1since the shape thereof is complicated and fluid-tightness is requiredfor an engaging portion.

With regard to the shape of the tubular catchment part 1, it is possibleto adopt one shown in FIG. 1 in which the cross-section in the verticaldirection with respect to a longitudinal direction thereof isrectangular, or it is possible to make it in other polygonal shapes, acircle, an oval, and so forth.

Although the membrane module connection part 3 may be one in which holesfor connecting to membrane module are formed on a flat plate-shapemember, it is possible to make it as one having a protruded shape asshown in FIG. 1. It is preferable to make it a protruded shape in termsof decreasing torsion during its formation and maintaining precision.Also, when the protruded shape is adopted, it is preferable to formadjacent protruded portions so as to be connected via a linking member 5since this increases the strength thereof.

FIG. 2 is a diagram showing a cross-sectional view of a catchment headeraccording to an embodiment of the present invention. As shown in FIG. 2,it is preferable to form one tubular catchment part 1 by connecting aplurality of members in series since a catchment header of arbitrarylength can be easily obtained.

In an example shown in FIG. 2, one block of the tubular catchment part 1has a size in which five membrane modules can be connected, and eachblock has a projection at one end thereof so that it may befluid-tightly engaged with the inside of the adjacent block via sealingmembers 7. A flange portion is fixed to the both ends thereof. Thefiltered liquid outlet 4 is disposed at one end or both ends of theflange portion.

If the number of the membrane modules that can be connected to one blockbecomes too large, the length of the block becomes too long. If thenumber of the membrane modules that can be connected is too small, onthe other hand, the number of blocks becomes too large and henceeconomically inefficient. Accordingly, the number of the membranemodules that can be connected to one block is preferably 5 to 20, andmore preferably 7 to 15.

Note that the method for connecting the adjacent blocks is notparticularly limited, and may be suitably selected, depending onassemble workability and intended use, from a mechanical connectingmethod, a heat melting connection method, a connecting method using anadhesive, and so forth. The mechanical connecting method may bepreferable in consideration of ease of disassembly and recycling.

Examples of the mechanical connection methods include screw fastening,fastening using pins and retaining rings, snap fitting, press fitting,caulking, and so forth. As for the screw fastening, loosening ofconnection due to creep of a resin, and creep destruction due to toomuch tightening must be considered. Assembly may be easy when the snapfitting method is adopted; however, a spring force must always beapplied to the claw to achieve sufficient fluid-tightness, and hence itis necessary to design the structure by taking into account the stressgenerated at the base portion of the claw. Accordingly, among thesemechanical connection methods, the fastening using pins and retainingrings which does not generate constitutive remaining stress at connectedportions of molded members is particularly preferable.

As for the sealing member 7, an O-ring, a flat packing, a V-ring, etc.,may be employed; however, use of an O-ring having high reliability insealing property is preferable. The material used for the sealing member7 may be suitably selected, depending of intended use, from a nitrilerubber, a styrol rubber, a fluorinated rubber, and so forth.

The cross-sectional area of the tubular catchment part 1 perpendicularto the longitudinal direction is preferably 4 to 36 cm², more preferably9 to 25 cm², since the pressure loss would become large and it becomesdifficult to increase the filtration amount if the area is too small,and the catchment efficiency would be reduced if the area is too large.

A reinforcement member 6 is disposed around the tubular catchment part1. The shape of the reinforcement member 6 is not necessarily limited aslong as a required strength can be obtained; however, it is preferableto arrange it so as to surround the tubular catchment part 1 around theshape of the outside of the tubular catchment part 1. Also, although thereinforcement member 6 can surround the entire tubular catchment part 1,it is preferable to arrange it so as to surround the portions thereofexcept the membrane module connection part 3 since the shape thereof canbe simplified in this manner.

Moreover, the reinforcement member 6 can be reticulated or in the formof a grid as long as it maintains a required strength.

The reinforcement member 6 prevents the catchment header from beingdeformed due to bending stress and torque applied to the catchmentheader, and the strength thereof, in terms of a Young's modulus which isexpressed as a ratio between stress and a length of torsion in thedirection of the stress, is 4.0 to 250 GPa when a stretching orcompressing stress vertical to the longitudinal direction of thereinforcement member 6 is applied.

The bending stress which is expected to be applied to the catchmentheader during its use is about 60-100 MPa. Accordingly, if the Young'smodulus of the reinforcement member 6 is less than 4.0 GPa, the strengththereof is insufficient for use over a long period. On the other hand,use of a material having a Young's modulus greater than 250 GPa is notpreferable since its hardness becomes too high to be fragile and it isextremely difficult to process such a material.

By arranging the reinforcement member 6 around the tubular catchmentpart 1, it becomes possible to use the tubular catchment part 1 havingthe Young's modulus of 4.0 GPa or less, and in this manner it becomespossible to make it compact and readily processed while maintaining thestrength of the catchment header.

Note that the Young's modulus is determined, depending on the materialused, in accordance with a testing method, such as JIS K7113 (a plastictensile testing method), JIS Z2241 (a metal material tensile testingmethod), and JIS K7073 (a carbon fiber reinforced plastic tensiletesting method).

It is preferable that the material used for the reinforcement member 6have an excellent anti-corrosion property, strength, and workability,and the material is preferably one of a metal, a filler reinforcedplastic, and a fiber reinforced plastic. Examples of the metal includestainless steel, titanium, aluminum alloy, magnesium alloy, etc., andexamples of the filler reinforced plastic and fiber reinforced plasticinclude one in which filler, glass fiber, carbon fiber, etc., iscontained in an ABS resin, a polyamide resin, a polycarbonate resin, apolyacetal resin, a denatured polyphenylene ether resin, etc. One havingthe above-mentioned range of Young's modulus can be suitably selectedamong these.

Although a membrane module to be connected is not particularly limited,it is preferable to use a flat plated shape membrane module when amembrane module unit is produced, since it is easily washed anddifficult to clog and can be used for filtration for a long period oftime in a stable manner. In particular, use of a hollow fiber membranemodule 12 shown in FIG. 3 in which a hollow fiber membrane 9 is expandedto be flat and an end portion thereof is fixed to a housing 11 using afixing member 10, is preferable since the catchment efficiency thereofcan be improved while maintaining an excellent cleaning property.

Examples of material used for the hollow fiber membrane include onewhich is conventionally known, such as cellulose, polyolefin,polysulfone, polyvinyl alcohol, polymethylmethacrylate, vinylidenepolyfluoride, polytetrafluoroethylene, etc., and use of a polyolefinmaterial having excellent stretching property, such as polyethylene andpolypropylene, is preferable from the viewpoint of workability,accommodation of vibrations during air diffusion, and so forth.

Although a method for connecting the membrane module to the catchmentheader is not limited as long as the fluid-tightness can be obtained, itis preferable to dispose an O-ring at a filtered liquid outlet of themembrane module and to fix it by inserting the filtered liquid outletinto a hole formed in the catchment header since the membrane filter canbe fixed in a fluid-tight manner with a simple procedure and detachmentof the membrane module becomes possible.

Although arbitrary number of catchment headers may be used in accordancewith the shape of the membrane module, the number of filtered liquidoutlets, etc., it is preferable that the catchment header be disposed sothat the flow of filtered liquid from each of the membrane modules tothe catchment header is as uniform as possible. For example, for thecase in which the filtered liquid outlet 8 is provided at both ends ofthe hollow fiber membrane as shown in FIG. 3, it may be preferable toprovide two catchment headers with one membrane module unit. Also,although the filtered liquid outlet 8 is disposed at one end of acatchment tube at both sides of the hollow fiber membrane in FIG. 3, itis possible to dispose the filtered liquid outlet 8 at both ends of thecatchment tube. In such a case, four catchment headers may be providedwith one membrane module unit.

Moreover, it is possible to provide the membrane module in a zigzagarrangement. In such a case, it is possible to use a catchment header inwhich holes for connecting to membrane modules are formed in a zigzagmanner, or two catchment headers may be arranged so as to be shiftedrelative to each other.

Note that when a membrane module unit is formed using a sheet shapehollow fiber membrane module which is expanded to be flat, it ispreferable to arrange it so that the sheet surface faces a verticaldirection from the viewpoint of cleaning efficiency. In such a case, thefiber axis direction of the hollow fiber membrane is arranged so as toface a horizontal direction or a vertical direction.

Hereinafter, the present invention will be concretely explained

EXAMPLE 1

An ABS resin (trade name: Diapet ABS, SW3, a product of Mitsubishi RayonCo., Ltd.) was subjected to injection molding and a tubular catchmentpart having a structure shown in FIG. 2 and a substantially squarecross-sectional area in a vertical direction with respect to alongitudinal direction was produced.

The number of membrane modules to be connected to one block was 10, andfour blocks were connected via sealing members of O-rings formed of aNBR rubber. The adjacent flanges were fixed using 4 mm screws.

The shape of the flange portions was substantially a square of 4×4 cmhaving a thickness of 4 mm. A filtered liquid outlet was attached toboth ends of the tubular catchment part via sealing members of O-ringsformed of a NBR rubber, and was fixed using 4 mm screws.

A stainless steel plate having a Young's modulus of 200 GPa and athickness of 1.5 mm as a reinforcement member was folded so as tosurround the overall length of the tubular catchment part except themembrane connection parts, and the height, width, and length thereofwere, 4.5 cm, 4.5 cm, and 84 cm, respectively.

The distortions in the horizontal and vertical directions of thecatchment header obtained in this embodiment with respect to the lengthdirection thereof was 1.5 mm or less in both horizontal and verticaldirections.

Also, the maximum bending moment of the catchment header when auniformly distributed load of 9.8×10⁻² N/m was applied was 0.9 N·m, andthe maximum bending stress was about 87 MPa, which is less than ⅕ of thestress that can lead to failure. Accordingly, the catchment headerpossesses a strength sufficient so as not to break during use.

INDUSTRIAL APPLICABILITY

According to the catchment header of the present invention, since atleast a part of the tubular catchment part is covered with areinforcement member having a Young's modulus of 4.0 to 250 GPa, alight-weight and compact catchment header which has excellentworkability and dimensional accuracy, and has sufficient strength, isobtained. Accordingly, a solid-liquid separation process using aseparation membrane can be stably carried out over a long period oftime.

1. A catchment header allowing a plurality of membrane modules to beconnected thereto, comprising: a tubular catchment part having a Young'smodulus of 4.0 GPa or less for collecting and removing filtrated liquidfrom the membrane modules, and a reinforcement member having a Young'smodulus of 4.0 GPa to 250 GPa which covers at least a part of saidtubular catchment part.
 2. A catchment header according to claim 1,wherein said tubular catchment part is formed of a synthetic resin.
 3. Acatchment header according to claim 1 or 2, wherein a cross-sectionalarea of said tubular catchment part perpendicular to a longitudinaldirection of the tubular catchment part is 4 to 36 cm².
 4. A catchmentheader according to any one of claims 1 or 2, wherein said tubularcatchment part comprises a plurality of members which are connected inseries.
 5. A catchment header according to any one of claims 1 or 2,wherein said reinforcement member is formed of a metal, a fillerreinforced plastic, or a fiber reinforced plastic.
 6. A catchment headeraccording to any one of claims 1 or 2, further comprising: a connectionpart having a protruded shape and that is adapted to be connected to amembrane module.
 7. A catchment header according to claim 6, whereinsaid connection part is linked to an adjacent connection part that has aprotruded shape via a linking member.
 8. A membrane module unit,comprising: a plurality of membrane modules, and a catchment headeraccording to any one of claims 1 or 2 to which said plurality ofmembrane modules are connected.
 9. A membrane module unit according toclaim 8, wherein said membrane modules are hollow fiber membrane modulesin which bundle ends of a hollow fiber membrane of a sheet shape areaccommodated inside a housing of a rectangular shape and arefluid-tightly fixed using a fixing member.
 10. A catchment headeraccording to claim 3, wherein said tubular catchment part comprises aplurality of members which are connected in series.
 11. A catchmentheader according to claim 3, wherein said reinforcement member is formedof a metal, a filler reinforced plastic, or a fiber reinforced plastic.12. A catchment header according to claim 4, wherein said reinforcementmember is formed of a metal, a filler reinforced plastic, or a fiberreinforced plastic.
 13. A catchment header according claim 5, furthercomprising: a connection part having a protruded shape and that isadapted to be connected to a membrane module.